The 3d printing of firearms is a challenge that both domestic law enforcement and international governance bodies have been concerned about for years.

As of last Friday, California is now requiring the owners of any gun that's been 3d printed to register that firearm with the State.

"There are no provisions in existing law that prevent a person from buying an 80 percent lower receiver and then making it into a fully functional firearm,"a California Senate analysis concluded. "Because 80 percent lower receivers are not considered firearms, a person purchasing them does not have to go through a federal firearms dealer, and does not have to undergo a background check. This bill is intended to close this loophole."

What the bill intends to do is force the State's citizens to place a detectable marker onto any homemade or 3d printed gun. Because many homemade guns are made of plastic, they can be undetectable at airports and other secure locations using metal detectors. The bill also prevents people from transferring or selling 3d printed guns, and any owner of a 3d printed firearm will also need to go through standard background checks in the State of California.

The ban on transfers and sales of 3d printed firearms was pushed through the legistlature in part by arguing that the quality of these firearms is too low and therefore inexperienced users are putting themselves in danger.

"Homemade guns may be of very poor quality and extremely unsafe and should therefore only be for personal use," theCalifornia Chapters for the Brady Campaign to Prevent Gun Violence said back in May. "At this point, many 3-D printed guns explode when they are fired. The technology will, no doubt, improve but it is unlikely that these guns would ever meet basic firing or drop tests and such unsafe guns should not be transferable."